In many manufacturing processes, adhesives having high tack, an extended open time, pot stability, and dimensional and biological stability after use are needed. Specifically, in the manufacture of books such as catalogs or paper covered books, during which two or more preliminary page assemblies, signatures, which include approximately 10 to 40 pages, are brought together in a first step in book manufacture. The signatures are clamped and held, stacked, rough cut to form the shape of the book, and a small film of primer is applied to the signature backs. The primer provides a surface that can readily accept additional adhesives used in book assembly and can also act in providing a flexible hinge-like film on the spine of the book. The primer is dried and a pick up adhesive is applied to the dry primer film. The pick up adhesive must have sufficient open time and rapid tack such that a light contact between the adhesive and the cover is sufficient to initially bond the cover to the signature back with sufficient integrity such that the cover remains in place without additional attachment means until the book can be finished in subsequent manufacturing stages in which the cover can be crimped and trimmed, completing the manufacture.
In the manufacture of hard cover books, in an operation known as case making, cover materials, generally fabric or coated fabric, are applied onto a cardboard cover material having two cardboard endboards connected with a center strip to form the hard book cover. Typically the adhesive is coated on the cover material and the end boards are contacted with the adhesive coating. After application, the cover material is folded back over the cardboard and is held in place by the adhesive. Just after manufacture, the cover material has the tendency to spring back or unfold and return to its original flat state. In order to prevent spring back, the case making adhesive needs to have a quick high tack. At least 4 to 10 seconds of open time is needed to provide enough time for assembly. After the cover is assembled and attached to the book, changes in humidity in the book environment and changes in the adhesive due to age can result in dimensional instability, resulting in a warpage or curling of the book cover.
In the past, animal glues have been used in book manufacture in steps such as cover pick up and case making operations. Animal based protein containing glues have adequate adhesive properties and have the benefits that they are moderate in cost and can be used in the cover pick up operation. Animal glues often do not seriously smear or stick to cutting means during book manufacture. However animal glues have certain drawbacks. Animal glues commonly gel at about 150.degree. F. At the gel point the glue changes from a fluid to a rapidly setting gel. The gel can become an adhesive after the water in the gel is removed during evaporation, but before evaporation the gel has low tack and little adhesion. Further, animal glue tends to be subject to substantial heat degradation resulting in a short pot life. The animal glues often can have an extremely short open time, and after drying can be inflexible. Further, animal glues exposed to high or low humidity can fail to be operative since in high humidity the animal glue dries much too slowly, while in low humidity rapid evaporation can remove an excess of water from the glue resulting in substantial loss of adhesion and flexibility. Animal glues fail to wet many surfaces which can result in non-uniform bonding and are incompatible with many substances used in book manufacture. Book covers made with animal glue can have dimensional instability in changing conditions of humidity, and can be subject to biological attack by insects and microorganisms.
Accordingly, a substantial need exists for a wholly synthetic replacement for animal glue. Further, a substantial need exists for a replacement for animal glue in paperback and hard cover book manufacture.